The present invention relates to a method and apparatus for drilling long and straight holes in rocks by means of a drill rig that may be aligned by means of a laser beam, which drill rig comprises a hollow drill stem with a pressure device for guiding the drill stem in a correct direction on applying pressure against the wall of the drilled hole.
Cutting of rocks and ore in mines, both above and benath ground, mainly is performed by drilling and blasting.
Investigations have shown that the costs of cutting can be reduced substantially if the technology concerning the drilling of long holes at a high precision can be mastered. In present day hole drilling operations the lengths of the holes are limited by large hole deviations, which means that it hardly can be foreseen where a hole will end.
Thus, a requirement for using longer drill holes and also for increasing the distance between holes is that a new drilling technology must be made available, thus making it possible to drill holes with a substantially higher precision than is obtainable today.
At present, drilling precision is limited by the stability and accuracy of the drill rigs being used, and how accurately the rigs can be adjusted in relation to a reference coordinate system.
The present development in this respect is directed to developing drill rigs with better rigidity and stability so that the drill stem can be started in the direction which is as correct as possible. Such drill rigs may improve the drilling accuracy to some extent, but fundamental limitations exist with respect to this technology.
Firstly, an uncertainty will remain with respect to the start direction of the drill. Besides, the drill stem may change direction on its way due to different reasons, such as:
inhomogeneities, slips etcetera in the rock PA1 distortions in the drill stem PA1 influence of gravity, etcetera.
Increasing of rigidity and stability requires more costly drill rigs. Additionally, accuracy depends on wearing of the equipment, and on the operator as well.